1. Field of the Invention
This invention relates to preservative compounds, and more particularly, to monobromodinitrile and dibromodinitrile compounds having bromine atoms positioned alpha to the nitrile groups, which exhibit excellent preservative activity, and to a method of making such new and useful compounds.
2. Description of the Prior Art
A well-known preservative for personal care products is 1,2-dibromo-2,4-dicyanobutane (also named 2-bromo-2-bromomethylglutaronitrile), which is sold as Merguard(copyright) 1200 (Calgon) or Integra(copyright) CG-20 (International Specialty Products). This specific dibromodinitrile compound is prepared by adding bromine to the double bond of 2,4-dicyanobutene (xcex1-methyleneglutaronitrile), as shown below: 
See U.S. Pat. Nos. 3,833,731; 3,877,922; 3,929,858; 4,655,815; 4,964,892 and 5,034,405.
Accordingly, it is an object of this invention to provide new and useful bromodinitrile preservative compounds which exhibit excellent preservative activity in such use compositions as personal care, nutritional, industrial and pharmaceutical compositions, and in which all bromine atoms therein are positioned alpha to a nitrile group.
Another object herein is to provide a method of making such novel preservative compounds.
These and other objects and features of the invention will be made apparent from the following description thereof.
Described herein are new and active preservative compounds which are particularly useful in personal care, nutritional, industrial and pharmaceutical products, having the general formula: 
where:
X and Y are H or Br, with at least one of X and Y being Br;
R is H or CH3; and
n=1-8; and
mixtures thereof.
These preservative compounds are particularly characterized by having all bromine atoms positioned alpha to the nitrile groups.
The preferred compounds of the invention are those wherein n=1 or 2.
Specific compounds of the invention have the formulas given below: 
2-bromo-4-methylglutaronitrile 
2-bromo-2-methylglutaronitrile 
2,4-dibromo-2-methylglutaronitrile 
2-bromoglutaronitrile 
2,4-dibromoglutaronitrile 
2-bromoadiponitrile 
2,5-dibromoadiponitrile 
2-bromosebaconitrile 
2,9-dibromosebaconitrile
Admixtures of compounds within the general formula, or the specific compounds, are also within the purview of the invention.
The preservative compounds of the invention are made by brominating a compound of the formula: 
where R and n are as defined above, with one or two equivalents of liquid bromine and a catalytic brominating agent, preferably phosphorus tribromide. For some products, N-bromosuccinimide or 1,5-dibromo-3,3-dimethylhydantoin can be used with a radical initiator (e.g., azobisisobutyronitrile or benzoyl peroxide).
The active preservative compounds of the invention can be included in personal care, nutritional, industrial or pharmaceutical compositions, suitably at advantageous use levels of about 0.01-1 wt %.